With the development of the mobile phone, more functions are supported by the mobile phone. For example, a touch panel is employed by a smart phone/high-end feature phone to allow a large-sized display screen to act as part of a user interface. In other words, the touch screen can display information and receive the user input. Besides, additional sensors, including a G-sensor, a magnetic field sensor, a light sensor, an orientation sensor, etc., may be employed by the smart phone/high-end feature phone to enhance the user experience.
However, when the user uses the smart phone/high-end feature phone to make an outgoing call or receive an incoming call, the touch screen is generally close to user's face during the call. The smart phone/high-end feature phone may receive an unexpected user input via the touch screen in the proximity of user's face. For example, the smart phone/high-end feature phone may end the call after misjudging that the soft key “End call” is touched by the user. If the size of the touch screen is larger, the probability of the misjudgment is higher. To solve this problem, a proximity sensor is therefore introduced. The conventional proximity sensor can operate in several different ways. One technique involves generating a constant beam of infrared light and measuring the reflection of the light to check for an object in close proximity. Therefore, when the proximity sensor detects that there is an object (e.g., user's face) close to the touch screen, the touch screen is disabled. In this way, the smart phone/high-end feature phone is prevented from receiving a user input via the touch screen when the user is using the smart phone/high-end feature phone to communicate with a contact person. When the call is ended or the proximity sensor detects that the object (e.g., user's face) is far away from the touch screen, the touch screen is enabled again to allow reception of the user input.
The conventional proximity sensor is a hardware element, which increases the production cost of the mobile phone inevitably. Thus, there is a need for an innovative design which is capable of providing the proximity detection function without using any conventional proximity sensor.